For instance, Patent Document 1 and Patent Document 2 disclose canned linear motor armatures and canned linear motors that have been hitherto used for the table feeding in the semiconductor manufacturing apparatuses or the machine tools, in which an armature winding is covered by a can and a refrigerant is supplied to flow through a refrigerant passage provided between the armature winding and the can, thereby recovering a heat generated from the armature winding by the refrigerant and reducing the temperature rise of a surface of the linear motor. Here, the linear motor disclosed in the Patent Document 1 will be described below with reference to the drawings.
Patent Document 1: JP-A-2002-27730 (page 4, FIG. 1)
Patent Document 2: JP-A-2000-4572
FIG. 16 is an entire perspective view of the canned linear motor showing a related art. In FIG. 16, reference numeral 10 designates a stator, 11 designates a case, 12 designates a can, 13 designates a bolt screw for fixing the can, 14 designates a pressing plate, 15 designates a terminal base, 16 designates a refrigerant supply port, 17 designates a refrigerant discharge port, 18 designates an armature winding, 25 designates a movable element, 26 designates a field yoke support member, 27 designates a field yoke, and 28 designates a permanent magnet. One movable element 25 includes the two flat plate shaped field yokes 27, the permanent magnets 28 respectively attached to the surfaces of the field yokes 27 and a total of four field yoke support members 26 inserted between the two field yokes 27, and has a hollow space part whose both ends are opened. The above-described permanent magnet 28 has, a plurality of magnets that are arranged adjacently on the field yoke 27 so that polarities are alternately different. The movable element 25 is supported by a linear guide or a static pressure bearing guide using balls and composed of sliders and guide rails not shown in the drawing.
Further, the other stator 10 has armatures arranged in the hollow space part of the movable element 25 so as to be opposed to the permanent magnets 28 of the movable element 25 through magnetic gaps. The detail thereof will be described below by referring to FIG. 17.
FIG. 17 is a front sectional view of the canned linear motor in the related art taken along a line A-A of FIG. 16. FIG. 18 shows a structure of an inner part of the stator except the can 12 in FIG. 17. In FIGS. 17 and 18, the stator 10 includes the frame shaped metallic case 11 having a hollow inner part, the plate shaped can 12 having the outer shape of the case 11 to cover the hollow part of the case 11 therewith, the bolt screws 13 for fixing the can 12 to the case 11, the pressing plate 14 having through holes of the bolt screws 13 to press the can 12 by an equal load, the three-phase armature winding 18 forming the armature arranged in the hollow part of the case 11, a winding fixing frame 19 for fixing the armature winding 18, an O ring 21 formed to be slightly larger than the edges of the case 11 and the can 12 and bolt screws 23 for fixing the winding fixing frame 19 to the case 11. As the material of the can 12 and the winding fixing frame 19, a resin is employed. Here, a thermosetting resin such as an epoxy resin or a thermoplastic resin such as polyphenylene sulfide (PPS) is used. The form of the cavity part of the case 11 is configured so as to surround the outer periphery of the armature winding 18. The armature windings 18 are arranged on both the surfaces of the winding fixing frame 19 formed in a flat plate shape. The winding fixing plate 19 formed integrally with the armature windings 18 is arranged in the hollow part of the case 11 and fixed to the case 11 by the bolt screws 23. On the edges of the front and back sides of the case 11, circulating grooves are provided and the O rings 21 are provided therein. Then, the cans 12 are arranged on the front and back parts of the case 11 so as to cover the case 11 therewith. The pressing plate 14 is laid on the can 12 along the edge of the case 11 and fastened by the bolt screws 13 so that the can 12 is fixed to the case 11. The armature winding 18 is composed of a plurality of groups of coils having concentrated winding coils prepared for three phases and attached to both the sides of the winding fixing frame 19. An electric power is supplied to the armature winding 18 from the terminal base 15 attached to the case 11. The terminal base 15 is electrically connected to the armature winding 18 by a lead wire (not shown in the drawing). Fun her, a refrigerant is supplied from the refrigerant supply port 16 provided in the case 11 and discharged from the refrigerant discharge port 17. During that time, the refrigerant is allowed to flow in a refrigerant passage 20 located between the armature winding 18 and the can 12 to cool the armature winding 18 that generates heat.
In the canned linear motor constructed as described above, a three-phase alternating current corresponding to the electric relative position of the movable element 25 and the stator 10 is supplied to the armature winding 18 so that a thrust is generated in the movable element 25 by an action on a magnetic field formed by the permanent magnet 28. Thus, the movable element 25 moves in an advancing direction shown by an arrow mark in FIG. 16. At this time, since the armature winding 18 in which heat is generated by a copper loss is cooled by the refrigerant supplied to the refrigerant passage 20, the rise of the surface temperature of the can 12 can be suppressed.